What's the difference???

[hibbert6]

I am looking at a Mercury ad that shows specs for all their outboards.

They typically make 3-5 models out of each block of a given displacement: for example, their 4 cyl, 105.7ci (1.7L) engine comes in 135hp, 150 hp, 175hp and 200hp models. Bore, stroke, compression ratio are all the same. How do they get 50% more HP out of that same block??? And how do they justify charging $3500 more (28%) for that extra HP? Is it just supply and demand?

If it's just a bigger carb, couldn't someone just upgrade the carb and re-tune to accomodate?

Dave

 

[JUSTINTIME]

Re: What's the difference???

carb intke and exhaust maybe

 

[hibbert6]

Re: What's the difference???

carb intke and exhaust maybe

Would that make that much difference?

Dave

 

[MercFan]

Re: What's the difference???

There was a long discussion about this a while back. It was regards the old in-line 6s, but I suppose the principles remain the same.
What it basically boiled down to was that the specs you mentioned is about the only thing that is the same. The reed valves differ, the pistons differ, the carbs differ, also the porting differs.

 

[jimmbo]

Re: What's the difference???

On a 4 stroke, things like cam profile, valves, head design, intake manifold design, carbs, supercharger boost on some models.

 

[hibbert6]

Re: What's the difference???

So, what you're saying is that a different "grind" or shape of some part - camshaft, ports, etc. - which costs no more to do or make, but is just different, allows more HP and so the manufacturer charges a bundle more for it?

 

[roozterdvx]

Re: What's the difference???

Generally speaking....horsepower costs money.

Whether is a marine application or automotive, engines are designed around certain parameters. Look at the smallblock Chevy engine for instance, you can find mid-70's vintage "smog" 350 cid engines wich produce only 150hp or so and the 1970 350 cid LT1 engine which came in the Corvette was rated at 370hp, same block essentially. The difference was the higher hp engine wasbuilt with better internals to produce and survive at higher power. Same thing applies in marine engines, although the rough casting may be the same, the crankshaft, rods, pistons, etc. are usually stronger for the higher hp. Intake manifold designs vary, port designs are optimized, etc.
Remember, an engine is essentially an air pump, and if all else were equal, and you made no changes except change fuel quantity to alter power level, then the engine would run lean , or rich. There are many variableswhich need to be optimized for each power level a given "engine family" produces, and it's the cost of development, as well as production that the consumer has to pay. Unfortunatley, we are a materialistic society, we crave more, and we are willing to pay for it. Especially when you consider that our hobby is not considered a necessity, (can you believe the nerve of some people?), but is considered a luxury.